1. Field of the Invention
This invention relates to a constricting device for the footrest ring of a chair, particularly to one provided with a conical constricting unit assembled between the conical sleeve of a footrest ring and the center tube of a chair. By mutual restraint and relative pressing of the conical sleeve of the footrest ring and the conical constricting main body of the constricting unit, the footrest ring can be firmly fixed on the center tube of the chair and conveniently adjusted in position.
2. Description of the Prior Art
As commonly known, chairs are indispensable to a family and an office. Some chairs are provided with soft seats for a user to sit thereon with comfort, others are respectively provided with an arc-shaped backrest according to ergonomics and still others are respectively assembled with armrests at the opposite sides for a user's hands to be comfortably set thereon. In addition, some high chairs are respectively disposed with a footrest ring for a user's feet to comfortably rest thereon. These above-mentioned additional designs of the chair enable a user to sit comfortably in the chair for a long time.
A conventional high chairs or desk chair provided with a footrest ring includes a sleeve secured in the center of the footrest ring to be fitted on the center tube of a chair. The sleeve of the footrest ring is diametrically bored with a threaded hole for a screw member to be inserted therethrough for fixing the footrest ring on the center tube of the chair when the bolt is turned tight and has its inner end pressing against the center tube. However, the way of the screw member pressing against the center tube for fixing the footrest ring on the chair has the following defects.
1. Generally, the center tube of a chair is a smooth round tube, and the footrest ring is fixed with the center tube of the chair only by having the inner end of a crew member pushing against the center tube with point contact; therefore, when the footrest ring is pressed downward by a treading force greater than the sustaining force of the screw member pressing the center tube, the footrest ring will be unable to bear such a treading force and likely to drop down.
2. Most conventional footrest rings are integrally made of plastic in order to economize cost; therefore, after the footrest ring is used for a long period of time and has its threaded hole repeatedly collided with the screw member due to treading force, the spiral teeth of the threaded hole will be deformed and damaged, so the footrest ring may become loosened to fall off.
3. The footrest ring of the chair can be adjusted in position by unscrewing or screwing tight the screw member with a wrist force, but this is no easy job for women or children.